Rechargeables for Wireless

Shure UK Senior Applications  Engineer, Tom Colman explores rechargeable battery options for wireless  microphones - moving from standard disposable batteries to modern  integrated rechargeables.

Wireless microphones and in-ear monitor systems  all need power from somewhere. Traditionally, wireless operators use a  standard portable cell in the form of familiar alkaline dry cell  batteries. They might not be great for the environment, but they are  easy to obtain and very reliable. It's only relatively recently that  explorations into rechargeable options for wireless systems have met the  standards required for professional use. More on this later, but let's  first look at the historic standard:

Standard Batteries

Alkaline batteries will discharge at a very linear rate, meaning  power will reduce evenly throughout the life of the battery. So let's  say we have a fully charged battery with five indicator bars. In the  case of alkaline disposable batteries, power will discharge at the  same pace when at bar five or bar one.

In the case of standard consumer rechargeable batteries, the battery  performance is much less predictable. The discharge rate is not linear  and is likely to reduce faster towards the end of the battery cycle.  This unpredictability makes standard consumer rechargeable batteries  unsuitable for professional productions.

Lithium Ion Rechargeable Batteries

Knowing the historic issues with rechargeable technology, we (Shure)  set out to develop a reliable rechargeable system for the professional  audio industry during the development of our high-end Axient wireless  system. The result was an advanced power management system — based on  medical-grade Lithion Ion cells — that introduced real-time monitoring  and lifecycle management to batteries and chargers. Since the launch of  Axient around five years ago, much of this advanced wireless technology  is now available (where possible) across the Shure portfolio of wireless  systems.

Taking Axient as the example, these purpose-built, modern  rechargeable systems give us far more reliable performance and essential  data to help ensure peace of mind. Utilising a built-in microchip, the  Axient system is able to deliver real-time readings of various key  data-points:

• Battery Health - The overall capacity of our battery compared to when it was new.
• The current charge (measured in 1% increments)
• Cycle Counts: This represents the amount of times  our battery has completed a full cycle from 100% down to 0% and back up  to 100%. This reading is cumulative, meaning it could also represent a  cycle of 100% down to 90% repeated ten times. It's estimated that when a  battery has completed 500 cycles it will still have a battery health  reading of around 80%. That's a lot of AA batteries saved from landfill!

By using a microchip in each battery, we know exactly how much  capacity is remaining through a real-time reading in hours and minutes.  This reading is accurate to within 15 minutes, and therefore, if your  battery is showing 1-hour remaining and the event is 30 minutes long,  you can be confident the battery will last for the duration.

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